RSH-4

Introduction
The RSh-4 kit (РШ-4 - Развернутая шихта тип 4 = Expanded cartridge type 4), although officially designated as EO-16 in its original manual, was first introduced in the very late '50s (1958-1960) and remained in service with the armed forces of the USSR until the fall of the country in 1991. It was intended to replace the older MO-2 and MO-4 kits.

Many countries of the Warsaw Pact copied the design of this Soviet kit.The most notable examples are the Polish SzM-41M, Bulgarian BSS-MO-4U and East German SchM-41M.

Kit
The basic kit includes:

The additional elements are: Additonally, in the case of special roles of the soldiers (marksman, communications etc.), two more facepieces are part of the kit. The two facepieces are the ShMS (ШМС) and the MM-1 (ММ-1). Since both facepieces use a voice emitter, a tin box of identical shape of the one containing the anti-fogging inserts is added to the kit. This additional box contains two spare communication membranes, so that the voice emitter can be repaired. The tin box is marked with an "M".
 * EO-16 (RSh-4) big dimensions filter
 * Type A bag (Сумка тип А)
 * Insulating lenses
 * One sided anti-fogging inserts NP (НП), 59mm diameter
 * Anti-fogging stick (КПЗО)
 * ShM-41MU (ШМ-41МУ) helmet-style facepiece
 * Corrugated hose
 * For ShMS (ШМС) facepiece:
 * Double sided anti-fogging inserts NPN (НПН), 44mm diameter
 * Replacement membranes for the voice emitter (M)
 * For MM-1 (ММ-1) facepiece:
 * Pair of optical inserts, to be installed before the first use (for protection and anti-foggimg)
 * Replacement membranes for the voice emitter (M)

Lastly, since the kit itself does not provide any protection from carbon monoxide, the DP-1 canister would be added if the situation required its use.

EO-16 (RSh-4) Big Dimesions Fiter
The EO-16 filter is a device used to filter out harmful and hazrdous dusts, particles, fumes, gasses and mists. These can be of nuclear, bacteriological and chemical origin.

The EO-16 filter outer case is composed of a 17,5x10,7 cm cylinder. On all its circumference there are 9 protruding rings, which help giving the whole canister a better resistance to physical damage. On top of the filter there is a screw cap with a 40 mm thread (GOST type), which seals the outlet port of the filter with the help of a rubber plug. On the bottom of the canister there is the inlet port, which is also threaded. This 40 mm thread allows the operator to attach the filter to the internal NBC filtration system of an armoured vechicle (BTRs, tanks). On the canister there are markings, which show the filter designation, production date and serial number. Example:
 * -ЕО-16- (Designation)
 * VII-77-22 (Month, year of production and serial number)

This is the standard format for the markings. It should be noted that, as with many Soviet equipment, these may vary between manufacturers.
 * В 801 (Batch number)

The inside of the filter is composed of three sections. The first section is the one further away from the center of the canister. This section contains a filtering paper that stops all solid dusts and particles from reaching the user (most notably nuclear fallout). The second section contains activated charcoal, which is responsible for the deactivation of chemical substances and all mists, gasses and vapours of biological nature. This section is separated from the first section by a circular grid. Such grid has many small holes that prevent the activated charcoal from escaping its intended position. Lastly, the third and most inner section is composed of a small cylinder, which is made of the same metal grid as the one between the first and second section. The grid stops the charcoal but lets the air move. Inside this cylinder there is another small layer of filtering paper, which prevents any charcoal dust small enough to go through the metal grid from reaching the user's lungs. The filter cannot be used in an atmosphere with less than a 17% oxygen volume.

''' WARNING: All EO-16 filters are at least 20 years past their expiration date, they WILL NOT provide any protection. The following information is taken from historical manuals and should be considered only as historical and technical data. '''

Technical sheet: The filter must also protect from industrial substances.
 * Air flow - 1,8 m³/h
 * Air resistance - 12,5...15,5 mm WG

With: the filter will perform in the following manner: The EO-16 filter does not provide any protection from carbon monoxide. For this reason, the DP-1 specialised filter is added to the EO-16 canister. This is done by screwing the outlet hole of the bigger canister to the threaded bottom of the DP-1 filter.
 * 1) Air temperature - 18...25C°
 * 2) Relative humidity - <75%
 * 3) Air flow - 30 l/min

Type A Bag (Сумка тип А)
The type A bag is a simple canvas bag, which is used to carry the whole kit. It is divided into three, main internal pouches and a small pocket. The foremost pouch is used to carry the hose when the kit is disassembled. The right pouch, located on the back, is used to carry the EO-16 filter. For this reason, on the bottom of the pouch, there are two small wooden sticks, which are used to keep the bottom of the filter lifted above the canvas surface of the bag, which might plug the inlet hole of the filter, creating a greater breathing resistance. The left pouch, located on the back of the bag, is used to carry the facepiece, which is folded in a way to protect the glass lenses. In the middle, between the two main left and right pouches, there is a small pocket, which is used to carry the anti-fogging and spare membranes tin boxes and the KPZO anti-fogging stick. On the outside of the bag there is a small pocket, which is used to carry the IPP-51 decontamination kit. It should be noted that, although rarer, there are versions of this bag that are fitted with a bigger external pouch, which is designed to carry the IPP-8 decontamination kit. Officially, the kit should be carried in a specific way, so that it can be considered "combat ready" and be donned quickly during an attack. This method of storage is shown in this picture.

As with all Soviet equipment, there are many variations of this bag. For this reason the colour, type of fabric, type of buttons and materials may vary, but they still all fall under the "Type A" cathegory of bag, which is marked by the "ГОСТ 13016-67" GOST number.

Insulating Lenses (НМУ - Накладные утеплительные манжеты)
The "NMU" insulating lenses are additional protective lenses. They are applied over the normal lenses of the facepiece with a rubber gasket. This gasket presses against the metal clamps of the facepiece, creating a tight seal.

The purpose of the NMU insulating lenses is to protect the fogging and water mist present on the inside surface of the eye lenses from freezing in cold temperatures. This layer of water mist is normally present inside the facepiece due to the moisture contained in the human breath. The NMU lenses create an insulating layer of air between the facepiece and the outside, preventing the freezing process. These lenses are used only when the outside temperature drops below a certain point (possibly -20 C°).

Anti-fogging Inserts ( НП - Незапотевающие пленки)
Anti-fogging inserts are circular devices that are applied on the inside of the facepiece, in order to prevent the creation of mist on the surface of the lenses. They are effective in temperatures from -40 C° to +40 C°. Anti-fog inserts consist of a colorless polyethylene terephthalate brand PET-100-BN TU 6-41-1576-93 or undyed polyethylene terephthalate-based brand "M", 175 microns thick, as per GOST 24234. A layer of desiccant is applied (100-120 microns) on one or both sides of the inserts. The standard diameter of the inserts is 59 mm, altough other sizes are available (56,5 mm and 44 mm). Smaller inserts are used with optical masks (44 mm inserts are designed for the ShMS facepiece). Inserts are stored inside small metal boxes, which are either marked as "НП" for the ones that are coated on only one side or "НПН" for double-coated inserts. The metal box is sealed with tape, which is

either made of white fabric, black fabric or blue PVC. The tape is essential in providing an airtight seal, in order to prevent humidity from reaching the inserts, which would damage their the anti-fogging coating. Each box contains 6 inserts, for a total of 3 pairs.

Anti-fogging Stick KPZO (КПЗО- карандаш против запотевания очковых)
KPZO sticks are designed to prevent misting of gas mask lenses. It consists of a small wax stick cointained inside a

bakelite case.

The wax is applied on the inside of the lenses with circular motions, until the whole surface of the lens is coated with wax. The bakelite case is designed to create an airtight seal, which protects the wax from drying. It should be noted that, during the production of these bakelite cases, different colours were used.

ShM-41MU (ШМ-41МУ) Facepiece
The ShM-41MU ("ShM" being "Шлем Маска", which means "Helmet Mask") is the standard facepiece used with the RSh-4 kit. It is a typical Soviet helmet-style facepiece, which covers the entire head of the wearer.

It consists of three main components: the rubber facepiece, the valve assembly and the lenses.

The rubber facepice is made of a white/grey latex mixture. This mixture is sensitive to UV rays, which make the rubber become of a brown colour after a prolonged exposure under the sunlight. A black version of the rubber mixture was created in the '70s. Such rubber is generally more flexible and softer compared to the traditional grey one. It is also more resistant to sunlight damage. The black version of the facepiece is extremely rare due to its limited production time and due to the fact that most of these masks were sent to countries like Vietnam and Egypt in the form of military aid.